Process for the reclamation of film scrap with permanganate solutions



Patented Sept. 5, 1933 UNITED STATES PROCESS FOR THE RECLAMATION OF FILMSCRAP SOLUTIONS WITH PERMANGANATE Thomas F. Murray, Jr., and Cyril J.Staud, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester,New York N. Y., a corporation of No Drawing. Application May 24, 1930.Serial No. 455,450

4 Claims.

This invention relates to a process for the reclamation of photographicfilm scrap and more particularly to a process for reclaiming film scraphaving a base of a cellulose derivative which has been dyed.

In substantially all methods for the recovery of film scrap, the silverhalide emulsion is first removed from the film scrapby soaking the scrapin hot water for a short length of time to loosen the emulsion from thescrap. This leaves the film base or support, which may be composed ofeither cellulose nitrate or cellulose acetate. This film scrap base isthen normally either (1) leached with an alcohol solution or (2)bleached and then, leached. The bleaching step has heretofore beenaccomplished with various compounds which liberate free chlorine,namely, calcium hypochlorite, sodium hypochlorite, hypochlorous acid, orcombinations or equivalents thereof. In some instances this treatment isnot entirely satisfactory for the reason that the free chlorine, as wellas the chloride, must be removed from the scrap before it can beutilized.

We have found that a good many of these seeming complications may beavoided if the film scrap from which the silver halide emulsion has beenremoved is bleached with a permanganate such as potassium or sodiumpermanganata-permanganic acid or a mixture of all or any of these.

The greatest'disadvantage in connection with permanganate bleaching is,however, that the permanganates are more costly than the hypochloritesfor the same weight of available oxygen. 7

In certain industrial processes there are, however, large quantities ofdilute acid permanganate liquors which cannot be longer used noreconomically recovered but which, so far as their oxidizing values areconcerned, are just as use ful as fresh solutions. These wastepermanganate liquors occur, for instance, in the process whereby exposedCine film is developed and redeveloped by what is known as the reversalprocess. This liquor has a permanganate content of from about .1% toapproximately 1%. When used directly on film scrap base, however, theseliquors are ineffective to completely remove the color therefrom evenafter several hours of treatment; some additional treatment was,therefore, found necessary.

We have discovered that these waste permanganate liquors may be utilizedfor the bleaching of film scrap base and other scrap if the scrap baseis first leached with dilute alcohol, followed by bleaching with thedilute permanganate solutions mentioned above. For instance, 'dyedcellulose acetate film scrap from which the silver halide emulsion hasbeen removed may be treated in a 50% methyl alcohol solution -for aboutthree hours and then washed with water, after which the scrap issubjected to treatment with a waste permanganate solution of thecharacter above described. It was found that after as short a treatmentas 15 minutes that the scrap was colorless.

Longer treatments up to one hour or even two hours or more may bedesirable where a particularly "deep color has to be removed. Thetemperature employed may be approximately room temperature, namely, fromabout 20 to 26 degrees centigrade. After the permanganate treatment, thescrap is removed and washed with water and then cleared in, forinstance, an acidified sodium bisulfite solution prepared by dissolving5 grams of sodium bisulphite in one liter of water and adding 5 cc of35% hydrochloric acid or an equivalent quantity of sulfuric acid.

It will be understood that in the case of cellulose acetate film scrapbase that the leaching so lution may consist of either a methyl or ethylalcohol mixture, and that the alcohol may be in the proportion of from70 to 30 per cent alcohol to from 30 to 70 per cent of water. The sodiumbisulfite solution is used merely to clarify the film scrap of anypermanganate compound and may be a rather dilute solution mildlyacidified. The product resulting from the permanganate oxidation may beremoved by equivalents of sodium bisulphite such as oxalic acid, sodiumnitrite, hydroxylamine, sodium hydrosulphite, sodium metabisulphite orother polythioic' acids or their salts.

In the event that it is desired to reclaim film scrap having a cellulosenitrate base the only precaution necessary is to not employ methylalcohol in the leaching solution, it being desired, of course, not toemploy in the leaching of either the cellulose nitrate or celluloseacetate base any leaching solution which is a solvent for the film base.

When alcohol is employed for leaching cellu lose acetate beforebleaching, it performs a diversity of functions, among which may bementioned: 1) removal of a portion of the dye present, if the same bealcohol soluble; (2) removal of any other alcohol soluble component ofthe material; (3) increasing the permeability of the surface layers ofthe material resulting in more ready penetrability of the celluloseacetate for bleaching solutions.

Also there are instances where it may be advantageous to employ alcoholfor leaching cellulose acetate after bleaching. By so doing we have theadvantage of (l) removal of the products of reaction; (2) removal ofalcohol soluble components of the material; (3) removal of residual dyewhich was not acted upon during bleaching if such dyes be alcoholsoluble. This leaching after bleaching need not be more fully set forthhere as approximately the same procedure is followed as when leachingbefore bleaching except that the time of treatment need not be quite aslong. i

What has been stated above concerning alcohol is to be construed asequally applicable to other non-solvents which are suitable for thispurpose and apparent to those skilled in the art.

It will thus be apparent that our invention is in fact two fold, namely,(1) the bleaching of dyed cellulosic derivative scrap and (2) theleaching of ing preceded by leaching as it may well be employed withoutprevious leaching althof the latter is to be preferred. Also thoseclaims directed more or less broadlyto leaching and bl'eaching are notlimited (unless so stated) to a bleaching step including the use of apermanganate as-it will be quite apparent that previous leaching willmake more easy the majority of bleaching pf'oc'' esses such as thosedisclosed in applications of Charles E. Allen filed i of even date, oreven the v usual hypochlorite or chlorine bleach as disclosed in theMiddleton Pater'it #1,743,155. r

of the invention will occur to those skilled in the this invention andthe scope of the claims a'ppended hereto. For

tive waste, such as dyed artificial silk waste which has a base ofcellulose nitrateor acetate.

What we claim as our invention and desire to Patent No. L925, 5641.

instance, the process isequally applicable to any dyed cellulosederiva-,

be secured by Letters Patent of the United States from the scrap.

2. The process of reclaiming dyed photographic cellulose acetate filmscrap which comprises pretreating the scrap to remove alcohol solublecomponents and to increase the permeability of the surface layersthereof by leaching with a 30-70% aqueous ethyl alcohol solution,washing the leached scrap with water to remove residual alcohol,decolorizing the washed scrap by subjecting it to the oxidizing actionof a .1-1.% solution of potassium permanganate, washing the bleachedscrap with water and thereafter clearing the scrap from traces of unusedpermanganate by subjecting it to the reducing action of an acidifiedsolution of sodium bisulphite.

3, The process of reclaiming dyed cellulose derivative scrap whichcomprises removing the alcoholsoluble components of the scrap byleaching it. with an alcohol which is non-solvent of the film scrap,whereby the alcohol soluble componcuts of the scrap are removed and thescrap is rendered porous, swollen and readily susceptible "tofurthefprocessing, decolorizing the scrap by subjecting it to theoxidizing action of a bleach 'f-ingsolution and thereafter removing fromthe scrap the products of the oxidation.

'4. The process of reclaiming dyed cellulose derivative scrap whichcomprises removing the alcohol soluble components of the scrap by leach-Numerous other variations and modifications ing. it with an aqueousalcohol which is nonsolvent of the film scrap, whereby the alcohol art,and it is intended that all modifications indlcated above and whichwould occur to those skilled,- in the art shall be included within thespirit of.

,soluble components of the scrap are removed and the scrap is renderedporous, swollen and readily susceptible to further processing, de-

colorizing the scrap by subjecting it to the oxidizing. action of apermanganate solution and thereafter removing from the scrap theproducts of the oxidation,

THOMAS P. MURRAY, JR. CYRIL J. STAUD.

September 5, loss.

rnonns r. nonnnr, am, iii At.

lit is hereby certiiied that erroraners in the printed specification oithe shove numbered parent requiring correction as iiollowsz' Page 2,time 79, claim 11, strike one the word "iilm"; and that the said LettersPatent should he read with this correction therein that the some mayconform to the record oi the case in the Parent @iiica (Moi) ii. iii.iiophino Acting (Coiooioner ,oi lPerenro.

